The OFDM (Orthogonal Frequency Division Multiplexing) modulation technique (hereafter referred to as OFDM technique) and the QAM (Quadrature Amplitude Modulation) technique are adopted in terrestrial digital broadcasting or the like. A modulation signal in the terrestrial digital broadcasting is formed of construction unit periods.
As an example of the conventional pre-compensation technique for nonlinear distortion, especially the technique of independent compensation for odd-order distortion, there is a technique described in Patent Literature 1. As the band of the signal becomes broad, the so-called memory effect in which distortion increases due to influence of the signal in the past becomes remarkable in general in a high-frequency power amplifier and hysteresis characteristics and even-symmetric distortion increases. And the circuit scale for the predistortion compensation becomes large. Therefore, a method for reducing the circuit scale of predistortion compensation which becomes large due to the memory effect of the high-frequency power amplifier is proposed in Non-Patent Literature 1. A predistortion compensation technique using an even-order time difference is disclosed in Patent Literature 2. A predistortion compensation technique using the amplitude differential and phase differential is disclosed in Patent Literature 3.
In the techniques described in Patent Literature 2 and Patent Literature 3, there is a drawback that it takes a time for the pre-compensation for reducing the memory effect to converge.